Coin-controlled automatic telephone-exchange system.



W. W. LBAGH. COIN CONTROLLED AUTOMATIC TELEPHONE. EXCHANGE SYSTEI.

APPLICATION FILED NOV. 1. 1906. v

Patented Aug. 25, 1914.

' men/wry ZQc'nfa'eZrZ 6122mm m, M 8 W WINFIELI) W. LEACH, OF CHICAGO,ILLINOIS, ASSIGNOR TO WESTERN.ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A

CORPORATION OF ILLINOIS. v

COIN-CONTROLLED AUTOMATIC TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented Aug. 25, 1914.

Application filed November 1, 1906.- Serial No. 341,517.

tem wherein the interconnection of subscribers lines is governed by thetentative payment or deposit of a coin at the calling station, and thefinal disposition of such coin is determined by the response or non-.response of the called subscriber.

My invention contemplates an arrangement of circuits and apparatuswhereby a subscriber initiatin a call is required to deposit a coin in acom collector at his station in orderto bring the calling device at hissubstation into the control'of the line selecting mechanism at thecentral otlice toconnect such line with the desired or called line.lVhen such selecting mechanism has connected acalling line with a calledline, and the'called subscriberresponds by removing his telephonefrom'its hook, electromagnetic mechanism is placed in operativecondition to automatically effect the final deposit of the coin in thecollector at the calling station when the calling subscriber at thetermination of the conversation hangs up his telephone. is busy, or theline is free and said subscriber fails to answer, means are providedwhereby the calling subscriber may obtain the refund of the cointentatively deposited. To this end I may provide a refund key which isoperative to refund the coin only when the telephone at the callingstation has been replaced on its hook after an unsuccessful attempt toobtain a connection, and which, when operated, transfers the coin into arefund chute leading to a refund tray on the outside of the coincollector.

A feature of my invention consists in the provision of means wherebywhen a calling line has been connected with a called line, theindividual line selecting mechanism of said called line will beautomatically disconnected from said line, and from the circult of theinterconnected subscribers, In

In case the called subscribers line--- carrying out this object, I mayprovide a cut-off relay in association with each line, arranged to beoperated only when the line is a called line, and only during connectionof said called line with the calling line to disconnect the individualselecting mechanism of such called line therefrom.

I will describe my invention more particularly by drawing, w ichrepresents diagrammatically an automatic telephone exchange systemembodying my invention, reserving, however, for-the appended claims astatement of the parts, improvements and combinations which I deem novelwith me.

Referring to the drawing, two telephone lines are shown extending inlimbs 1, 2, from substations, A, B, respectively, to a central office,where each line is provided with line selecting and connectingmechanism. I will describe in detail the circuits and apparatusassociated with the line of station A, it being understood that the lineof station B is equipped in exactly the same manner; and for convenienceof description I will consider station A as the calling station and'station B as the called station.

At the substation is provided the usual telephone apparatus in a bridgeof the limbs 1, 2. A calling device 3 is provided at the substation,comprising a springactuated arm 4 adapted to be set in a positionrepresenting the number of the line wanted, or a digit thereof, and tobe returned under the influence of a spring to operate a gear 5 ,tocausethe same to intermittently close a pair of contacts 6, 7,a number oftimes according to-the adjustment of the arm 4. The arm 4 while awayfrom normal position maintains open a pair of contact springscontrolling the substation bridge of the line.

The contacts 6, 7, control the operation of the central office lineselecting mechanism, these contacts being in turn controlled by a pairof normally-open contacts 8, 9, within the coin collector C,.which areclosed by a coin when tentatively deposited by a subscriber. The contactspring 7 is connected to earth, and the contact spring 6 is connectedwith a conductor 10 which leads through contacts 8.

v 9, within the collector,-

to the limb 2 of the line. The coin collector shown, which forms no partof the present invention, is provided with an electromagnet 11 in abranch 12 exreference to the accompanying tending from the limb 1 of theline to earth. The said magnet is arranged to be unresponsive to thecentral office battery current, bu t to require a high voltage currentfor its operation. Said magnet is provided with an armature 13 mountedupon the return. pole piece 14 of the magnet before the core there of.The armature carries on one side of its pivotal point thecoin-controlledcontacts 8, 9, while on the other side of said pivot thearmature is provided with a pin 15 connected with a retractile spring16,- the contact pins 8, 9 projecting within the coin chute in the pathof a coin. A pin 17 also projects through a slot in the wall of the coinchute, and together with pin 8, is adapted normally to support a coinplaced within the collector. Said pin 17 is mounted upon a flexiblesupport 18 which may be attached in any desirable way to the frame ofthe collector, said support 18 being adapted to be engaged by theplunger or refund key 19. The plunger 19 is maintained in its normalposition by a spring 20, and while in such position said plunger closesa pair of contact springs 21, 22 included in limb 2 of the line.

When a coin is placed within the collector, it engages the pins 17, 8,forcing said pin 8 into engagement with its contact 9, to complete thebranch conductor leading to the interrupter. In case the coin is to bedepos ited, the magnet 11 in attracting its armature 13 removes the pin8 from the path of the coin, which thereupon falls into the chute 23leading to the cash box. On the other hand, if a coin is to be refunded,the plunger may be operated and will engage and move the flexiblesupport 18, removing pin 17 from the path of the coin, allowing the cointo fall into the refund chute 24. If the calling subscriber, afterreceiving a connection, attempts to regain his coin by pushing in theplunger, the initial movement of said plunger opens the contacts 21, 22in the limb 2 of the line, which as hereinafter explained, will causethe operation of magnet 11 to deposit the coin.

At the central oflice, the limbs 1, 2 of the line pass through thearmatures 31, 32, respectively, of cut-ofi relay 33, to the contacts 34,35, upon the rotatable selector arm 36, the limb 2 extending through acondenser, armature 37 and its normally-open front contact of relay 38,through the armature 39 and back contact of relay 40, to the selectorcontact 35, while the limb 1 extends through a condenser, armature 41,and back contact of relay 40, to the contact '34. The third terminal 42upon the selector arm is connected with a conductor 43 leading throughthe winding of relay 38 to ground, said relay 3 being preferablysluggish in its action. The contact arm 36 is arranged to sweep overterminals which may be connected with the telephone lines or with trunklines leading to other selecting mechanism; In the present case, I haveshown the terminals as representing telephone lines, that is, each lineis provided with a set of three terminals, terminal 44 being connectedwith the limb l of the line, while the terminal 45 is connected with thelimb 2 of the line. The local terminal 46 of the set is connected withthe conductor 47, which leads through the cut-ofi? relay 33, to the freepole of grounded battery 48. The limbs 1, 2 of course are multiplied tocontacts upon the different selectors S in the exchange.

The selector arm 36 is mounted upon a vertical rotary shaft- 49 providedwith a ratchet 50 adapted to be engaged by a stepping pawl 51 operatedby an electromagnet 52, said ratchet being provided with a retainin pawl53 operated by a magnet 54. After the selector arm has been moved to theposition opposite the desired set of line ing mechanism, is provided ina bridge 57 of the limbs 1, 2, of the line, said bridge also including abattery 58, having its negative pole grounded, and a relay 59, saidbattery being interposed between the relays 56, 59, with its positive orfree pole connected with the limb 2 of the line. When the telephone isremoved from its hook at the calling station A, a circuit is completedby way of the bridge 57 for the relays 56, 59 and current also flowsfrom the tree pole of battery 58 through bridge 57, limb 2 of the line,through the substation bridge closed by the telephone switch 60, to limbl of the line, and thence to earth through branch 12, which includeselectromagnet 11 of the coin collector. Such current, however, doesnotaffect the magnet 11 of the coin collector. The relay 56 is providedwith a sluggish armature 61, which is adapted when attracted to close ashunt 62 about the cut-off relay 33 of the calling lineto prevent itsimproper actuation if such line should be selected and tested by anotherline during conversation.

Line selecting 0pemt-i0n.The armature 63 of relay 56 controls thecircuits of the selectin mechanism, the armature being connecte with theconductor 64, which extends to the free pole of battery 58, while thefront contact of said armature is connected with a conductor 65, whichleads through the retaining magnet 54 and stepping magnet 52 in series,through normally closed contacts 66, 67, controlled by relay 55, throughthe armature 68 and back contact of busy test relay 69, to earth.

A branch conductor 70 leads from conductor 65 through the winding ofconnecting magnet 55, through a pair of contacts 71, which are intermittntly made and broken by the armature bf the stepping magnet in itsoperation, back to the con ductor 65. Said contacts 71 are arranged toprevent, while being rapidly made and broken, the energizaticn of theconnecting magnet55, but when the stepping magnet 52 remains energizedfor a period longer than the interval between steps, as when selectionhas been completed, the back contact 71 will slowly follow up and makecontact with the front contact 71, and thereby reestablish the circuitthrough the connecting magnet 55, which, since the circuit is alsoclosed through the armature 63 of the relay 56, causes the connectingmagnet 55 to be energized. It is to accomplish the closure of thecontacts 71 upon a prolonged energization of the relay 52, as justdescribed, that the back contact 71 is arranged pivotally mounted asindicated upon the drawings. The magnet 55 is provided with an armature72 connected by a conductor 73 with the said conductor 70.-

Said armature, when attracted, forces the shaft 49 downwardly, andengages spring 67 to separate the same from'its anvil 66,

to thereby complete, a circuit for magnet 55 independent of the contacts71.

The calling subscriber at station A, in initiating a call, deposits acoin in the collector 'C, which falls upon the stops 17, 8, closing thecontacts 8, 9. He thereupon operates the calling device to make andbreak the contacts 6, 7, a predetermined number of times, according tothe number of the line desired, and a circuit is intermittently mad'eand broken for the relay 56 at the central oflice, said circuitextending from the free pole of battery 58, through relay 56, bridge 57,limb 2 of the line, contacts 8, 9, closed by the coin, through thecontacts 6, 7, of the calling device. Relay 56, in vibrating itsarmature 63, intermittently makes and breaks a circuit cxtending fromthe free .pole of battery 58, conductors 64 and 65, through retainingmagnet 54, and stepping magnet 52,

through the springs 66, 67, through the armature 68 and back contact ofbusy test relay 69 to earth. The retaining magnet 54 is operated tothrow the pawl 53 into engagement with the ratchet 50, and also thestepping magnet 52 operates to rotate the shaft 49 and bring theselector arm into po sition opposite or over the set of terminalsrepresenting the line desired. \Vhen the contact arm 4 of the callingdevice returns to normal position, after operating contacts 6, 7, itcloses again the metallic circuit of the limbs 1, 2, maintaining therelays 56, 59, energized, and current flows from the free pole ofgrounded battery.58 through con ductors 64, 65, 70, through connectingmagnet through the contacts 71, which are now at rest, back to conductor65, and thence to earth through the armature 68 and back connected withthe limb. 1 of the line.

contact of relay 69. Su'liicient current now flows in this circuit tooperate the connecting magnet 55, which attracts its armature 72, forcinthe shaft 49 downwardly, and bringing the terminals 34, 35, 42, intoengagement with the terminals 45, 44, 46, representing the called line.-The'armature 72 also engages contact spring 67 to separate the same fromits anvil 66, and completes a completed from the free pole of groundedbattery 48, through cut-ofi" relay 33 of the called line, conductor 47,terminals 46, 42, upon the selector, conductor 43, to earth throughrelay 38. In case the called line is free, the relay 33 is operated anddisconnects from the called line its individual line selectingmechanism, but if said line is busy, by virtue of its being a callingline, the cutofl relay 33 will not be operated, due to the presence ofthe shunt 62 thereabout closed by its line selecting relay 56. In casethe called line is already in use as a called line, the relay 33 will,of course, already have been operated.

Busy z est.The limb 2 of the line is normally open at the armature '37and front contact of sluggish relay 38, which is included in the circuitabove traced, and a testing conductor extends from the terminal 35 uponthe selectorarm, through the limb 2 of the line to the armature 37 ofrelay 38, whose back contact is connected with a conductor 74 leadingthrough a winding 75 of the busy test relay to earth. In case the calledline is busy there will. 'bepotential upon the terminal 44 from thecentral ofiice battery 58 by way of the substation of the line, andcurrent will flow through the testing conductor and winding '75 -of busytest relay. 69 to earth and energize said relay before the sluggishrelay 38 has had time to respond to the current in the local circuit-47-43 before traced. The relay 69 when thus energized 'attracts itsarmature v68, opening the circuit 6465-707365 of the connecting magnet55, and allowing the selector mechanism to be restored to normalcondition by means of a suitable spring. Said relay 69 is also providedwith an armature 76, which is connected with a conductor 77 leadin tothe front contact of an armature '78 o? relay 56, said armature 78 beingThe front contact of armature 76 of relay 69 is connected with aconductor 79 which leads through the winding 80 of relay 69, through thesecondary winding of a busy tone apparatus 81, to the free pole ofgrounded battery 82. And when said relay 69 is energized, due to saidtesting current, and the armatures are given their initial attractivemovement, current flows from the free pole of grounded battery 82through the winding 80 of said relay, armature 78 and front con-- Thesubscriber, upon hearing the busy tone in his telephone, hangs up hisreceiver and thereby causes the deenergization of relay 56, whichretracts its armatures, the armature 78 opening the locking circuit ofthe busy tone relay 9 and restoring the same to normal position.

Calliny a free h'nc where subscriber (mswers.-In the present condition,when the contacts upon the selector rest in engagement with theterminals of the called line, there is no potential present upon thecontact terminal 44, and the testing conductor receives no current; thesluggish relay 38, however, which is included in the local circuit43-47, completed by contacts 42, 46, is operated, and cuts ofl? theconductor 74, which includes the winding of the test relay, from thelimb 2 of the line, at the same time completing the continuity of saidlimb. The relay 38 is provided with an armature 83 which is connected toground, the front contact of said armature being connected with aconductor 84 which leads through the relay 40 to the free pole of agrounded battery 85, and said relay 38,

' when attracted, in case the called line is free, completes a circuitto operate relay 40, which thereupon attracts its armatnres 39, 41,whose front contacts form the terminals of a conductor 86, including aringing generator 87 and the winding 88 of a relay 89. Thus, when therelay 40 1s energized,.ringing current flows from the upper pole, forexample, of'the generator 87 throu h the armature 41' and front contactof re ay 40, line conductor '1, contacts 34, 45, upon the selector, limb2 of the called line, thence through the bell at the substation of thecalled line, back over limb 1 of'the called line, through the contacts44, 35, of the selector, limb 1 of the calling line, armature 39 andfront contact of relay 40, through the winding 88 of the relay 89, tothe lower pole of the generator 87. The relay 89 is arranged to beunresponsive to the current flowing in the circuit just traced, owing tothe high resistance in the line at the substation, but when the calledsubscriber responds by removin his telephone from its hook, a shunt isesta lished about the bridge containing the bell and condenser at thesubstation, and the winding 88 is enabled to energize the magnet 89sufliciently to attract its armatures 90, 91. The armature 90 of relay89 is included in a conductor 100, which leads from the free pole ofgrounded battery 85, through a low resistance winding 92 of relay 89,while the front contact of said armature is connected with a conductor93, which leads through the armature 94 and front contact of relay 59 tothe bridge 57 and earth. The conductors 100, 93 and 57 act as a shuntabout relay 40, to cause the same to retract its armatures 39,

'41, and break the ringing circuit above traced, the relay 89 beinglocked up by means of its winding 92 included in said shunting circuit.A bridge 95 of the limbs 1, 2, of the line is provided between thecondensers and the contacts upon the selector, said bridge containing abattery 96 between impedance coils to furnish the talking currentrequired by the called station for transmission purposes.

Deposit of the coin.-The armature 91 of the relay 89 is arranged to besluggish in its movement, said armature being connected,with a conductor97 leading through the back contact of armature 78 of relay 56 to thelimb 1 of the line, while the front contact of said armature 91 isconnected with a conductor98 leading through a generator 99 to earth.when the relay 89 is operated upon the response of the calledsubscriber, the armature 91, in responding, places" the generator 99 incondition to operate the magnet 11 to deposit the coin when the callingsubscriber at the termination of the conversation hangs up histelephone. lVhen the calling subscriber hangs up his telephone therelays 56,59, are deenergized to break the locking and connectingcircuits above traced, including the locking circuit of relay 89. Butthe armature 91 of relay 89, being sluggish, remains in its attractedposition for an instant after the retractive movement of the armature 78of relay 56, whereupon current flows from generator 99 by way ofconductors 98, 97, limb 1 of the line, through the electromagnet 11 ofthe coin collector to earth. This current causes the electromagnet 11 toattract'its armature 13, removing stop 8 from the path of the coin,which thereupon falls into the depositing chute 23.

Refund of c0z'n.1n case the called subscriber is busy, or fails toanswer, the calling subscriber may hang up his telephone and operate theplunger 19, which will engage the flexible support 18 and remove pin 17from the path of the coin, which thereupon falls into the refund chute24. If the calling subscriber, after the called party answers, attemptsto regain his coin by operating the plunger, the initial' movement ofsaid lunger opens the springs 21, 22, break: ing t e line circuit andcausing the denergization of the relay 56, whose armature 78 in itsretractive movement completes a circuit from the generator 99 by way ofcon ductors 98, 9?, limb 1 of the line, branch 12 to earth through thecoin collector magnet 11, which thereupon operates to deposit the coin.

It will be understood, of course that various forms 'of coin collectorsmay be used with the system of my invention. It should also be statedthat while several batteries are shown, for convenience of illustration,a single central battery-may be employed.

I claim:

1. The combination with a calling and a i called telephone lineextending from substations to a central oflice, of a toll device at thesubstation of the calling line, auto matic means at the central oflicefor uniting said lines, operable from the'calling station, upon thetentative operation of said toll device, and automatic means for finallycomleting the cycle of operations of said toll (evice, controlledjointly in the response of the called subscriber and in the replacementof the calling subscribers telephone.

2. The combination with a calling and a 4 called telephone lineextending from substations to a central oflice, of,a toll device atthecalled subscriber,

the substation of the calling line, automatic line selecting mechanismat the central ofiice operable upon the tentative operation of said tolldevice for uniting said lines, a magnet for said toll device connectedwith the calling line adapted to finally complete the cycle ofoperations of said toll device, a relay at the central oliice, anoperative circuit for said relay controlled in the response of a sourceof current for operating said ma net, and means controlled jointly bysaid relay andin the restoration of the calling station apparatus tonormal condition, for connecting said source of our rent with the lineto operatesaid magnet.

3. The combination with a calling and a called telephone line extendingfrom substations to a central office battery, of a switch at eachsubstation controlling the line circuit thereof, a toll device at thesubstation of the calling line, automatic line selecting mechanism atthe central oflice, operable upon the tentative operation of said tolldevice for uniting said lines, a magnet for said toll device connectedwith the calling line adapted to finally complete the cycle ofoperations of said toll device, a source of current. for operating saidmagnet, a relay in the calling line circuit responsive to saidsubstation switch, an armature for said relay, a relay having a sluggisharmature, an operative circuit for said relay completed upon theresponse of the called subscriber, and

means actuated upon the attraction of the sluggish armature, and theretraction of the armature of said first-mentioned relay, when saidsubstation switch is opened, for connecting said source of current withsaid line to operate said magnet and complete the cycle of operations ofsaid toll device.

4. The combination with a calling and a called telephone line extendingfrom substations to a central otfice battery, of a switch at eachsubstation controlling its line circuit, a relay at the central oflicein the line circuit of said calling line, a toll device at the callingstation, automatic line selecting mechanism at the central. ofiiceoperable upon the tentative operation of said toll device, for unitingsaid lines, an

elctromagnet for said toll device connected with the calling line andadapted to finally complete the cycle of operations of said to'lldevice, a relay at the central ofiice operative upon the response of thecalled subscriber, a source of current for operating saidelectro-m'agnet, a conductor for connecting said source with the line tooperate said electromagnet, and contacts for closing saidconductor,actuated upon the operation of said last-mentioned relay and thequiescence of the relay in the calling line circuit.

5. The combination with a calling and a called telephone line extendingfrom substations to a central office, of a toll device at the substationof the calling line, automatic line selecting mechanism at the centraloflice, operable from the calling station upon the actuation of saidtoll device thereat, a source of ringing current, automatic mechanismactuated when said lines are united for applying said ringing current tothe called line, and automatic means operated upon the response of thecalled subscriber, for cutting off said ringing current from the calledline.

6. In a telephone exchange system, the combination with a calling and acalled telephone line extending from substations to a central oflice, ofa tolldevice at the substation of the calling line, automatic lineselecting mechanism at the central oflice operable from the callingstation upon the operation of said toll device at the calling stationfor uniting said lines, a source of ringing current, and meansautomatically actuated when said line selecting mechanism connects withthe called line for applying said ringing current thereto.

7. In a .telephone' exchange system, the combination with a calling anda called telephone line extending from substations to a central oflice,of a toll device at the substation of the calling line, automatic lineselecting mechanism at the central ofiic'e operable from the callingstation upon the operation of said toll device at the calling stationfor uniting said lines, a source of ringing ourrent, means automaticallyactuated when said line selectin mechanism connects with the called linetor applying said ringing current thereto, and means automaticallyoperated upon the response of the called subscriber for cutting off saidringing current from the'line.

8. The combination with a calling and a called telephone line extendingfrom substations to a central ofiice, of a toll device at the station ofthe calling line, automatic line selecting mechanism at the centraloflice operable from the station of the calling line upon the tentativeoperation of said toll device thereat for connecting said lines, asource of ringing current, means automatically operated when connectionis made with the called line for connecting said ringing current wit-hsaid line, means operated in the response of the called subscriber forcutting oii said ringing current, and means controlled in the responseor non-response respectively of said called subscriber to governdiiferent final operations of said toll device.

9. The combination with a calling and a called telephone line extendingfrom substations to a central office, of a toll device at the substationof the calling line, automatic line selecting mechanism at the centralofiice operable from the calling station upon the tentative operation ofsaid toll device thereat for uniting said lines, a source of ringingcurrent, means automatically operated upon the connection of said linesfor applying said ringing current to the called line, means operated inthe response of the called subscriber for disconnecting said ringingcurrent from the called line, means controlled jointly by the responseof the called subscriber and the restoration of the apparatus of thecalling substation to normal position for finally completing the cycleof operations of said toll device, and a refund key operative in casethe called subscriber fails to answer or his line is busy.

10. In an automatic telephone exchange system, the combination with acalling and a called telephone line extending from substations to acentral ofiice, of a toll device at the station of the calling line,automatic mechanism at the central office for uniting said lines,controlled from the calling station upon the tentative operation of saidtoll device, and means, actuated upon the replacement of the telephoneat the calling station, at the termination of conversation, forefi'ecting the final operation of said toll device.

11. In an automatic telephone exchange system, the combination with acalling and a called line, of a toll device at the station of thecalling line, automatic mechanism at the central oflice for uniting saidlines controlled from the calling station upon the tentative operationof said toll device, means controlled in the response of the calledsubscriber for determining the final operation of said toll device, andmeans operable by subsequently replacing the receiver on the hook at thestation of the calling line for efi'ecting such final operation of saidtoll device.

12. In an automatic telephone'exchange system, the combination with acalling and a called line extending from'substations-to a centraloiiice, of a toll device at the substation of the calling line,automatic means.

at the central otlice operable from the calling station upon thetentative operation of said toll device for uniting said lines,automatic means for controlling the completion of the cycle ofoperations of said toll device upon the response of the calledsubscriber, and a refund key 'for producing such final o eration of saidtoll device when actuated a ter the response of the called party, andfor producing a different operation of said toll device when operatedprior to the respone of the called party.

13. The combination with a calling and a called telephone line extendingfrom substations to a central office, of a toll device at the substationof the calling line, automatic line selecting mechanism at the centralofiice, a'toll deviceat the substation of the calling line, meanscontrolled by the tentative operation of said toll device at the callingstation for governing the operation of said selecting mechanism by thecalling subscriber to connect said telephone lines, automatic meanscontrolled in the response of thecalled subscriber for finallycompleting the cycle of operations of said toll device and manualmechanism operable independently of the receiver hook at the substationof the calling line for controlling the final operation of said tolldevice, said mechanism operating as a refund device when actuated priorto the response of the called party.

14. In a telephone exchange system, the combination with a calling and acalled-telephone line extending from substations to a central ofiice, ofa toll device at the substation of the calling line, automatic lineswitching mechanism at the central office, for uniting said lines,operable upon the tentative operation of said toll device, a source ofringing current, means automatically operated when the switchingmechanism unites with a called line, for applying said ringing currentthereto, means automatically operated when the called party responds,adapted to cut oil said ringing current, and mechanism controlledjointly by said means and by the calling party for completinggthe cycleof operations of said toll device.

15. In a telephone exchange system, the

combination With a calling and a called tele phone line extending fromsubstations to a central office, of a toll device at the substation ofthe calling line, automatic line switching mechanism at the centraloffice, for uniting said lines, operable upon the tentative operation ofsaid toll device, a source of ringing current, means automaticallyoperated when the switching mechanism unites with a called line, forapplying said ringing current thereto, a relay in said ringing circuitunresponsive to the normally high resistance at the called substation,and responding to the decreased ,resistance in the circuit when thecalled subscriber answers, means controlled by said relay, for cuttingoff said ringing current from the called line, and means actuated bysaid relay for controlling the completion of the cycle of operations ofsaid toll device at the calling station. i

16. In a telephone exchange system, the combination with a calling and acalled telephone line extending from substations to a central oflice, ofa toll device at the substation of the calling line, automatic lineswitching mechanism at the central ofli'ce, for uniting said lines,operable upon the tentative operation of said toll device, a source ofringing current, means automatically operated When the switchingmechanism unites with a called line, for applying said ringing currentthereto, a relay in said ringing circuit operated upon the response ofthe called subscriber, for cutting off said ringing current from theline, a locking circuit for said relay controlled jointly by said relayand the callin partys telephone hook, and means actuate by said relayfor controlling the operation of said toll device.

In Witness whereof, I hereunto subscribe my name this nineteenth day ofOctober WINFIELD WV. LEAOH. Witnesses:

IRVING MACDONALD, ALFRED H. MOORE,

